Local Anesthetics: Review of Pharmacological Considerations

Abstract

Local anesthetics have an impressive history of efficacy and safety in medical and dental practice. Their use is so routine, and adverse effects are so infrequent, that providers may understandably overlook many of their pharmacotherapeutic principles. The purpose of this continuing education article is to provide a review and update of essential pharmacology for the various local anesthetic formulations in current use. Technical considerations will be addressed in a subsequent article.

Local Anesthesia Part 2: Technical Considerations

“…In the cartridge, the local anesthetic solution exists in 2 ionic forms: the tertiary form ( B) and the quaternary form ( BH This is of clinical significance in that it is the tertiary form of the drug ( B) rather than the BH þ form that is lipid soluble and able to diffuse across the lipid-rich nerve membrane entering into the nerve, where it then picks up a H þ , which converts it into the quaternary form of the drug ( BH þ ), which then enters into sodium channels and blocks nerve conduction. 3 When a small percentage of B is available, the speed of onset of anesthesia would be considerably slowed were it not for the body's buffering capability. Once injected into the tissues, the natural process of buffering occurs.…”

“…We now have the ability to make local anesthetics work faster (buffering), to more rapidly reverse residual soft tissue anesthesia ( phentolamine mesylate [Oraverse]), 3 and to make injections more comfortable (eg, buffering, computer-controlled local anesthetic delivery systems such as The Wand and the Single-Tooth Anesthesia System).…”

“…More than 50% of medical emergencies occurring in dental offices happen during or immediately following administration of a local anesthetic. 2 An earlier paper by Becker and Reed 3 provided an indepth review of the pharmacology of these invaluable drugs. In the present paper we will discuss issues of importance to the safe and effective delivery of these drugs, including needle gauge, traditional and alternative injection techniques, an d methods to make injections more comfortable for patients (eg, warming, buffering, novel delivery devices).…”

Basic and Clinical Pharmacology of Autonomic Drugs

“…The use of epinephrine and levonordefrin for this purpose has been reviewed previously. 13 As epinephrine is absorbed from the site of injection, systemic cardiovascular effects will begin to appear and can be attributed to activation of all 3 classes of adrenergic receptors.…”

A Study of Clonidine and Dexmedetomidine as Adjuvant to Epidural Levobupivacaine for Post Operative Analgesia in Infraumbilical Surgeries

“…Neuraxial anaesthesia and analgesia provide potent analgesic effect by inhibiting nociceptive transmission from peripheral to central neuronal system, but their analgesic effect may be limited by the short half life of current local anaesthetics. The analgesic duration can be prolonged by increasing dose of local anaesthetics; however the risk of accompanied systemic toxicity can be increased [2] . Therefore, adjuvant can be added to local anaesthetics to prolong the analgesic duration and to limit the dose requirement of local anaesthetics.…”